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The BCL-2 family is centrally involved in the mechanism of cell death after cerebral ischemia. It is well known that the proteins of the BCL-2 family are key regulators of apoptosis through controlling mitochondrial outer membrane permeabilization. Recent findings suggest that many BCL-2 family members are also directly involved in controlling transmission of Ca 2+ from the endoplasmic reticulum (ER) to mitochondria through a specialization called the mitochondria-associated ER membrane (MAM). Increasing evidence supports the involvement of microRNAs (miRNAs), some of them targeting BCL-2 family proteins, in the regulation of cerebral ischemia. In this mini-review, after highlighting current knowledge about the multiple functions of BCL-2 family proteins and summarizing their relationship to outcome from cerebral ischemia, we focus on the regulation of BCL-2 family proteins by miRNAs, especially miR-29 which targets multiple BCL-2 family proteins. [ABSTRACT FROM AUTHOR]

Highlights: [•] Astrocytes and miRNAs are key players in cerebral ischemia. [•] Some miRNAs are astrocyte-enriched. [•] Targeting astrocyte-enriched miRNAs protects neurons from ischemia. [Copyright &y& Elsevier]

Abstract: Our prior work demonstrated that geldanamycin (GA) reduced injury due to oxygen-glucose deprivation (OGD) in primary astrocyte cultures. Using medium with an ionic composition similar to that observed during in vivo global ischemia, the selectivity and temporal profile of CA1 neuronal damage seen in vivo was mimicked with OGD in mouse hippocampal organotypic slice cultures. The present study tested the ability of GA to reduce delayed neuronal death in such cultures. Treating organotypic cultures with 100nM GA for 24h prior to OGD induced Hsp70 and significantly reduced CA1 neuronal damage. Staining with ubiquitin to identify protein aggregates revealed reduced redistribution of ubiquitin, consistent with reduced protein aggregation likely due at least in part to induction of Hsp70 by GA. [Copyright &y& Elsevier]

Mitochondria are central to both apoptotic and necrotic cell death, as well as to normal physiological function. Astrocytes are crucial for neuronal metabolic, antioxidant, and trophic support, as well as normal synaptic function. In the setting of stress, such as during cerebral ischemia, astrocyte dysfunction may compromise the ability of neurons to survive. Despite their central importance, the response of astrocyte mitochondria to stress has not been extensively studied. Limited data already suggest clear differences in the response of neuronal and astrocytic mitochondria to oxygen–glucose deprivation (GD). Prominent mitochondrial alterations during stress that can contribute to cell death include changes in production of reactive oxygen species (ROS) and release of death regulatory and signaling molecules from the intermembrane space. In response to stress mitochondrial respiratory function and membrane potential also change, and these changes appear to depend on cell type. Bcl-2 family proteins are the best studied regulators of cell death, especially apoptosis, and mitochondria are a major site of action for these proteins. Although much data supports the role of Bcl-2 family proteins in the regulation of some of these mitochondrial alterations, this remains an area of active investigation. This mini-review summarizes current knowledge regarding mitochondrial control of cell survival and death in astrocytes and the effects of anti-apoptotic Bcl-2 proteins on astrocyte mitochondrial function. [Copyright &y& Elsevier]

Many studies have demonstrated the protective effects of Bcl-xL against both apoptotic and necrotic cell death, but the mode of action of Bcl-xL remains unclear. This work analyzed effects of Bcl-xL overexpression on cellular levels of reactive oxygen species (ROS), intracellular calcium ([Ca2+]i), and mitochondrial membrane potential (ΔΨm) in cultured mouse primary astrocytes after exposure to glucose deprivation (GD) or hydrogen peroxide (H2O2). Upon exposure to GD or H2O2, uninfected and Lac-Z-expressing astrocytes showed an immediate, rapid increase in ROS accumulation that was slowed and or reduced by Bcl-xL. Changes in ΔΨm in response to the two insults differed. H2O2 induced a decrease in ΔΨm that was initially greater in Bcl-xL cells, but then held stable. ΔΨm in control and Lac-Z-expressing cells initially declined more slowly, but after about 20 min showed rapid deterioration. Five hours of GD caused mitochondrial membrane hyperpolarization followed by a decrease in ΔΨm, which was not observed with Bcl-xL overexpression. Bcl-xL failed to inhibit the calcium dysregulation seen in control cells exposed to 400 μM H2O2, but still improved cell survival. There was no increase in [Ca2+]i with 5 h of GD. These data thus dissociate the effect of Bcl-xL on calcium homeostasis from effects on ROS, ΔΨm, and for H2O2 exposure, cell survival. [Copyright &y& Elsevier]

• Stroke remains a major cause of death and disability worldwide. • Differences in sex and age play an important role in clinical outcomes. • Steroid hormones, differential cell death and immune pathways, and sexually dimorphic microRNAs may all contribute. Cerebral ischemia remains a major cause of death and disability worldwide, yet therapeutic options remain limited. Differences in sex and age play an important role in the final outcome in response to cerebral ischemia in both experimental and clinical studies: males have a higher risk and worse outcome than females at younger ages and this trend reverses in older ages. Although the molecular mechanisms underlying sex dimorphism are complex and are still not well understood, studies suggest steroid hormones, sex chromosomes, differential cell death and immune pathways, and sex-specific microRNAs may contribute to the outcome following cerebral ischemia. This review focuses on differential effects between males and females on cell death and immunological pathways in response to cerebral ischemia, the central role of innate sex differences in steroid hormone signaling, and upstreamregulation of sexually dimorphic gene expression by microRNAs. [ABSTRACT FROM AUTHOR]

Abstract: Protein aggregation and misfolding are central mechanisms of both acute and chronic neurodegeneration. Overexpression of chaperone Hsp70 protects from stroke in animal and cell culture models. Although it is accepted that chaperones protect cells, the mechanism of protection by chaperones in ischemic injury is poorly understood. In particular, the relative importance of preventing protein aggregation compared to facilitating correct protein folding during ischemia and recovery is not known. To test the importance of protein folding and minimize interaction with co-chaperones we studied the bacterial chaperonin GroEL (HSPD1) and a folding-deficient mutant D87K. Both molecules protected cells from ischemia-like injury, and reduced infarct volume and improved neurological outcome after middle cerebral artery occlusion in rats. Protection was associated with reduced protein aggregation, assessed by ubiquitin immunohistochemistry. Marked neuroprotection by the folding-deficient chaperonin demonstrates that inhibition of aggregation is sufficient to protect the brain from ischemia. This suggests that strategies to maintain protein solubility and inhibit aggregation in the face of acute insults such as stroke may be a useful protective strategy. [Copyright &y& Elsevier]